Battle.net BattleTag FAQ
Blizzard added a FAQ for the upcoming BattleTag feature to their new support site this afternoon.

Originally Posted by Blizzard
(Blue Tracker / Official Forums)

What is a Battle.net BattleTag?
A BattleTag is a unified, player-chosen nickname that will identify you across all of Battle.net – in Blizzard Entertainment games, on our websites, and in our community forums. Similar to Real ID, BattleTags will give players on Battle.net a new way to find and chat with friends they've met in-game, form friendships, form groups, and stay connected across multiple Blizzard Entertainment games. BattleTags will also provide a new option for displaying public profiles.

When will BattleTags go live?
We will soon begin limited testing of some features and functionality of BattleTags in the Diablo III beta test, and the feature will be available to Diablo III players at launch. BattleTags will be integrated into other Blizzard games and services such as World of Warcraft and StarCraft II at some point in the future, but we don't have exact rollout plans to share just yet.

Will my BattleTag be unique?
A player's BattleTag is not unique, so you won't need to worry about whether your preferred name is available. You can use any name you wish, as long as it adheres to the BattleTag Naming Policy. Only one BattleTag can be associated with each Battle.net account.

If my BattleTag isn't unique, what makes me uniquely identifiable? How will I know I'm adding the right friend to my friends list?
Each BattleTag is automatically assigned a 4-digit BattleTag code, which combines with your chosen name to create a unique identifier (e.g. AwesomeGnome#3592). Your BattleTag and code are viewable when you log in to the Battle.net website and within the Diablo III beta client, and can be shared with other players who want to send you a friend request manually. You will also be able to send BattleTag friend requests list within the context of a game (by clicking a person's BattleTag when he or she sends you a message, for example) without knowing their BattleTag code. In either case, each player must mutually agree to become BattleTag friends.

I'm not in the Diablo III beta – can I choose a BattleTag now anyway?
Sure! You can pick your BattleTag now through Battle.net Account Management, regardless of whether you're participating in the Diablo III beta test. Simply visit the BattleTag creation page (http://www.battle.net/account/manage...ag-create.html) to get started. Make sure to choose a handle you will be happy with in the long term and that abides by our BattleTag Naming Policy, as you will be unable to change your BattleTag once you've selected it. We plan to provide a way for players to change their BattleTags in the future, but we don't have any further details to share just yet.

Where will my BattleTag be seen?
During the Diablo III beta test, your BattleTag will be seen in the Diablo III client (on friends lists and in chat), on the Diablo III forums, and in Battle.net Account Management. In the future, expect it to be displayed in other Blizzard games like StarCraft II and World of Warcraft on friends lists, in chat, or when making posts on their associated forums. We'll have further details on how and where your BattleTag will be displayed in the future.

When will World of Warcraft and StarCraft II support BattleTags?
Our plan is for all current and future Blizzard games to support BattleTags eventually. However, we don't have any announcements to make regarding when BattleTags will be integrated into World of Warcraft or StarCraft II at this time.

Do I need to choose my BattleTag now?
You will only be required to create a BattleTag now if you'd like to log in to the Diablo III beta client (beginning with an upcoming patch) or to use a Diablo III-related identity on the Diablo III forums. You will still be able to post on these forums using a World of Warcraft or StarCraft II character name if you wish.

Will I still be able to display my character on my profile or Armory page?
Armory profiles will be unaffected by the introduction of BattleTags. We'll have more information on how BattleTags will be integrated into existing games in the future.

How will this affect World of Warcraft?
BattleTags will add a new way for you to make friendships and communicate in World of Warcraft. For example, you'll be able to create cross-game, cross-realm friendships with your BattleTag, similar to the way Real ID works now. We'll have more details to share closer to the feature's launch.

Will this affect my existing Real ID friendships?
No. Your Real ID friendships will continue to exist, and all of the features and benefits of Real ID will remain available to you. BattleTags will simply give players another way to connect and communicate across Blizzard games. For example, if two players aren't Real ID friends but want to stay in touch across Battle.net, they'll be able to establish a BattleTag-based friendship; in the future, BattleTag friends will have access to many of the communication benefits (such as cross-game chat) currently available to Real ID friends.

Do BattleTags replace Real ID? Can I create new Real ID friendships?
BattleTags are a new feature separate from Real ID. Real ID will continue to work as it always has, and you can continue to create Real ID friendships with people you know in real life.

Will this affect my World of Warcraft or StarCraft II character names in any way?
Your World of Warcraft character names will continue to exist and work as they currently do. We're still in the process of determining how we will handle StarCraft II character names once BattleTags are integrated into the game.

How does my BattleTag work in the Diablo III beta?
Only some BattleTag features will be available during the Diablo III beta test. At first, players will be able to add friends to their friends list using their BattleTags, though new or different features may be available at different times during the testing process. We'll have more information on all of the features of BattleTags in Diablo III with the launch of the game next year.

Just scrape the concept of RealID all together and just let this thing live?Doesn't seem all the different...Could we instead get some privacy options to either one of these systems? Like appearing offline to everyone or just one person? I'm really reluctant to add people to my RealID just for those single reasons that sometimes I just want to be left alone and do my stuff int he game without having annoying people in my friend list (which I may or may not know in real life).

The primary changes are the removal of the email address requirement, so you can "friend" people who you would not be happy to share an email address with.
You can also have a chosen tag, so that you can be identified by a familliar name rather than a real one which would mean nothing to someone else, or you simply want to keep to yourself.
If anything thats a huge improvement to privacy.

Yes I do agree that an "appear offline" or similar toggle would be welcome however, a feature I have discussed in the past.

You were only supposed to add people to Real ID you knew in real life.

This was a flawed and unwanted concept right out of the gate. You could here the virtual pin drop when they announced RealID. We were promised something really cool with all these bells and whistles. What we got was like "Um...what? Thanks...I guess..."

the battletag system is completely broken no matter what name I pick it says its inappropriate. Supposedly the expression checker for it is broken atm.
Hopefully they fix it soon as I can't use my d3 beta anymore and I dont wanna pick a tag and be stuck with it forever

So players will now be branded like cows, why doesnt Activision/blizzard just make a barcode tattoo on each of their costumers, i think thats the future.

Because Activision/Blizzard is only the financial entity that manages the resources of Activision and Blizzard Entertainment. Blizzard Entertainment is the entity you have design issues with. All platforms have gravitated to this concept to one degree or another. By in large it is only a convenience to everyone involved.